Add Istio example

[matheusfm]

Feature Description

Istio also uses CEL for custom metrics. I would like to suggest adding an example for Istio here.

Istio documentation: https://istio.io/latest/docs/tasks/observability/metrics/customize-metrics/#use-expressions-for-values

Is your feature request related to a problem?

No

What alternatives have you considered?

The examples are in the file: https://github.com/undistro/cel-playground/blob/main/examples.yaml

Additional Context

If you'd like to work on this or have questions, please comment below for more information.

[marcelloale]

Olá @matheusfm como poderia ajudar?

[matheusfm]

Hi @marcelloale
As described above, the proposed idea is to include an Istio example in CEL Playground, as Istio uses CEL for custom metrics.

You can find the file containing all the examples at https://github.com/undistro/cel-playground/blob/main/examples.yaml, and any new examples should be added there.

Each example consists of a CEL expression and input data.
To create a suitable example, you may need to explore Istio and Envoy.

[marcelloale]

I'm interested in working on this issue (#29) to add Istio examples. I noticed that the Istio documentation provides examples for access log filtering with CEL expressions in the section 'Configure access logs with Telemetry API' here.

Would it be appropriate to use these examples from the Istio documentation to implement 'Istio: Default Access Log Filtering' , or would that be outside of your preference?

[matheusfm]

It's a good approach to use the example

response.code >= 400 || xds.cluster_name == 'BlackHoleCluster' ||  xds.cluster_name == 'PassthroughCluster'

for Istio access log filtering.

Just remember to include the associated input data from the CEL Playground example to provide a more complete reference.